Difference between getExternalFilesDir and getExternalStorageDirectory()
JavaAndroidFileJava Problem Overview
I understand that ExternalFiles is to be used on API 8 and up and getExternalStorageDirectory is for 7 and down. However I am a little confused between the use. For example I wanted to check that a folder that exists and previously you would use something like:
File ChildFolder = new File(Environment.getExternalStorageDirectory() + "/ParentFolder/Child");
However every example I see says to use getExternalFilesDir (null), File.ext. Since I am above API 8 I want to use this method but how do I just check for a folder? I will check for a files existence at another point but for now just want to see if the folders exist??
Java Solutions
Solution 1 - Java
getExternalFilesDir()
It returns the path to files folder inside Android/data/data/your_package/ on your SD card. It is used to store any required files for your app (e.g. images downloaded from web or cache files). Once the app is uninstalled, any data stored in this folder is gone too.
getExternalStorageDirectory()
It returns the root path to your SD card (e.g mnt/sdcard/). If you save data on this path and uninstall the app, that data won't be lost.
Solution 2 - Java
First of all, we need to understand what is difference between Internal Storage, External Storage (aka primary external storage), and Secondary External Storage?
Internal Storage: is storage that is not accessible by the user, except via installed apps (or by rooting their device). Example: data/data/app_packageName
Primary External Storage: In built shared storage which is "accessible by the user by plugging in a USB cable and mounting it as a drive on a host computer". Example: When we say Nexus 5 32 GB.
Secondary External Storage: Removable storage. Example: SD Card.
getExternalFilesDir (String type)
It returns the path to files folder inside Android/data/data/your_package/ on primary external storage. Which is inbuilt storage.
Environment.getExternalStorageDirectory()
It will return the path of the secondary external storage directory
Solution 3 - Java
! IMPORTANT UPDATE ! for whoever comes across this question.
As this is a somewhat old question just wanted to provide some additional information. Since KitKat even apps that have WRITE_EXTERNAL_STORAGE permission are only allowed to write to Android/data/data/your_package/ on external storage, a.k.a getExternalFilesDir()
If you will try to write to getExternalStorageDirectory() + "/somefolder/anotherfolder/" you will get a SecurityException on most devices
Solution 4 - Java
!! IMPORTANT !!
Environment.getExternalStorageDirectory() is deprecated and Context#getExternalFilesDir(String), MediaStore, or Intent#ACTION_OPEN_DOCUMENT, should be used instead.
> This method was deprecated in API level 29. To improve user privacy, direct access to shared/external storage devices is deprecated. When an app targets Build.VERSION_CODES.Q, the path returned from this method is no longer directly accessible to apps. Apps can continue to access content stored on shared/external storage by migrating to alternatives such as Context#getExternalFilesDir(String), MediaStore, or Intent#ACTION_OPEN_DOCUMENT.
https://developer.android.com/reference/android/os/Environment.html#getExternalStorageDirectory()
Also beginning from Android.M developers need to ask for permissions at run time.
See more details in documentation here and this question